Guanfacine extended release in the treatment of attention deficit hyperactivity disorder in children and adolescents

Contemporary diagnosis and treatment of conduct disorder in youth

INTRODUCTION

Conduct disorder (CD) is characterized by repetitive and persistent antisocial behaviors, being among the most frequently reported reasons of referral in youth. CD is a highly heterogeneous disorder, with possible specifiers defined according to age at onset, Limited Prosocial Emotions (LPE) otherwise known as Callous-Unemotional (CU) traits, Emotional Dysregulation (ED), and patterns of comorbidity, each with its own specific developmental trajectories.

AREAS COVERED

The authors review the evidence from published literature on the clinical presentations, diagnostic procedures, psychotherapeutic and psychoeducational approaches, and pharmacological interventions from RCT and naturalistic studies in youth. Evidence from studies including youths with LPE/CU traits, ED and aggression are also reviewed, as response moderators.

EXPERT OPINION

Due to its clinical heterogeneity, relevant subtypes of CD should be carefully characterized to gain reliable information on prognosis and treatments. Thus, disentangling this broad category in subtypes is crucial as a first step in diagnosis. Psychosocial interventions are the first option, possibly improving LPE/CU traits and ED, especially if implemented early during development. Instead, limited information, based on low-quality studies, supports pharmacological options. Second-generation antipsychotics, mood stabilizers, and stimulants are first-line medications, according to different target symptoms, such as aggression and emotional reactivity. Developmental pathways including ADHD suggest a specific role of psychostimulants.

A Potential Role for Neuroinflammation in ADHD

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioural disorder in children and adolescents. Although increases in oxidative stress and disturbances of neurotransmitter system such as the dopaminergic and abnormalities in several brain regions have been demonstrated, the pathophysiology of ADHD is not fully understood. Nevertheless, ADHD involves several factors that have been associated with an increase in neuroinflammation. This chapter presents an overview of factors that may increase neuroinflammation and play a potential role in the development and pathophysiology of ADHD. The altered immune response, polymorphisms in inflammatory-related genes, ADHD comorbidity with autoimmune and inflammatory disorders and prenatal exposure to inflammation are associated with alterations in offspring brain development and are a risk factor; genetic and environmental risk factors that may increase the risk for ADHD and medications can increase neuroinflammation. Evidence of an association between these factors has been an invaluable tool for research on inflammation in ADHD. Therefore, evidence studies have made it possible to generate alternative therapeutic interventions using natural products as anti-inflammatories that could have great potential against neuroinflammation in ADHD.

The KCNH3 inhibitor ASP2905 shows potential in the treatment of attention deficit/hyperactivity disorder

N-(4-fluorophenyl)-N'-phenyl-N"-(pyrimidin-2-ylmethyl)-1,3,5-triazine-2,4,6-triamine [ASP2905] is a potent and selective inhibitor of the potassium voltage-gated channel subfamily H member 3 (KCNH3) that was originally identified in our laboratory. KCNH3 is concentrated in the forebrain, and its overexpression in mice leads to cognitive deficits. In contrast, Kcnh3 knockout mice exhibit enhanced performance in cognitive tasks such as attention. These data suggest that KCNH3 plays important roles in cognition. Here we investigated the neurochemical and neurophysiological profiles of ASP2905 as well as its effects on cognitive function, focusing on attention. ASP2905 (0.0313 and 0.0625 mg/kg, po) improved the latent learning ability of mice, which reflects attention. Microdialysis assays in rats revealed that ASP2905 increased the efflux of dopamine and acetylcholine in the medial prefrontal cortex (0.03, 0.1 mg/kg, po; 0.1, 1 mg/kg, po, respectively). The activities of these neurotransmitters are closely associated with attention. We used a multiple-trial passive avoidance task to investigate the effects of ASP2905 on inattention and impulsivity in juvenile stroke-prone spontaneously hypertensive rats. ASP2905 (0.1 and 0.3 mg/kg, po) significantly prolonged cumulative latency as effectively as methylphenidate (0.1 and 0.3 mg/kg, sc), which is the gold standard for treating ADHD. Further, ASP2905, amphetamine, and methylphenidate significantly increased the alpha-band power of rats, suggesting that ASP2905 increases arousal, which is a pharmacologically important activity for treating ADHD. In contrast, atomoxetine and guanfacine did not significantly affect power. Together, these findings suggest that ASP2905, which acts through a novel mechanism, is as effective for treating ADHD as currently available drugs such as methylphenidate.

Autonomic instability in a dehydrated child on guanfacine: Case report and literature review

An 8-year-old girl on guanfacine extended-release (GXR) for attention-deficit/hyperactivity disorder presented with somnolence, bradycardia and hypotension during a heat wave. No overdose was suspected. She was admitted to the intensive care unit for monitoring and ongoing fluid resuscitation for hypotension. Electrocardiogram showed intermittent atrioventricular dissociation. Upon restarting the drug post-discharge, blood pressures were normal, and follow-up electrocardiograms documented asymptomatic bradycardia but no dissociation. GXR is used as monotherapy or adjunct therapy in the treatment of inattention and hyperactivity in children. No published paediatric or adult study has documented atrioventricular dissociation, bradycardia or hypotension significant enough to warrant hospital admission. This case suggests that GXR can pose a hemodynamic risk to children in the context of elevated environmental temperatures and dehydration. Clinicians should be aware of this potential complication and should counsel patients about signs and symptoms of hypotension, bradycardia, bradypnea and somnolence.

α2-Adrenoceptors in the treatment of major neuropsychiatric disorders

Presynaptic autoreceptors mediate a retrograde transfer of information by a negative feedback mechanism mediated by the transmitter of the neuron, and fulfill an autoregulatory function in neurotransmission in the peripheral and central nervous system (CNS). Starting with norepinephrine (NE), it was later reported that an autoreceptor-mediated negative feedback mechanism exists for other neurotransmitters, including dopamine (DA), serotonin, acetylcholine, histamine, GABA, and glutamate. This feedback mechanism regulates calcium-dependent transmitter release and synthesis through terminal presynaptic autoreceptors, while the firing rate of the neuron is regulated through somatodendritic autoreceptors.

Profile of guanfacine extended release and its potential in the treatment of attention-deficit hyperactivity disorder

The α2-adrenergic receptor agonist guanfacine, in its extended-release formulation (GXR), is the most recent nonstimulant medication approved in several countries for the treatment of attention-deficit hyperactivity disorder (ADHD) as monotherapy and as adjunctive pharmacotherapy to stimulants in children and adolescents. The present paper aims to review comprehensively and critically the pharmacodynamic and pharmacokinetic characteristics and the published evidence on the efficacy and safety profile of GXR in the treatment of ADHD. A comprehensive search of relevant databases (PubMed, Embase, and PsycInfo) was conducted to identify studies published in peer-reviewed journals until January 15, 2015. Though the precise mechanism of action of guanfacine in the treatment of ADHD is not fully understood, it is thought to act directly by enhancing noradrenaline functioning via α2A-adrenoceptors in the prefrontal cortex. Weight-adjusted doses should be used, with a dosing regime on a milligram per kilogram basis, starting at doses in the range 0.05-0.08 mg/kg/day, up to 0.12 mg/kg/day. As evidenced in short-term randomized controlled trials and in long-term open-label extension studies, GXR has been shown to be effective as monotherapy in the treatment of ADHD. Furthermore, GXR has also been found to be effective as adjunctive therapy to stimulant medications in patients with suboptimal responses to stimulants. Many of the adverse reactions associated with GXR, particularly sedation-related effects, were dose-related, transient, mild to moderate in severity, and did not interfere with attention or overall efficacy. There are no reports of serious cardiovascular adverse events associated with GXR alone or in combination with psychostimulants.

Drug therapy of attention deficit hyperactivity disorder: current trends

Attention deficit hyperactivity disorder is a developmental disorder with an age onset prior to 7 years. Children with ADHD have significantly lower ability to focus and sustain attention and also score higher on impulsivity and hyperactivity. Stimulants, such as methylphenidate, have remained the mainstay of ADHD treatment for decades with evidence supporting their use. However, recent years have seen emergence of newer drugs and drug delivery systems, like osmotic release oral systems and transdermal patches, to mention a few. The use of nonstimulant drugs like atomoxetine and various other drugs, such as α-agonists, and a few antidepressants, being used in an off-label manner, have added to the pharmacotherapy of ADHD. This review discusses current trends in drug therapy of ADHD and highlights the promise pharmacogenomics may hold in the future.

Treatment for co-occurring attention deficit/hyperactivity disorder and autism spectrum disorder

Interest in the co-occurrence of attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) has grown in the last decade. Research on clinical populations supports the frequent co-occurrence of ADHD traits (e.g., hyperactivity) in individuals with ASD and ASD traits (e.g., social communication deficits) in individuals with ADHD. Similar trends in co-occurring traits have been observed in population-based samples, as well as family and genetic studies of affected individuals. Despite increased interest in co-occurring ADHD and ASD, relatively little research has been devoted to treatment considerations. The vast majority of intervention research has examined pharmacological treatment using traditional ADHD medications. Relatively few psychosocial interventions have directly addressed co-occurring symptoms. Treatment development will benefit from enhanced understanding of the phenomenon of co-occurring ADHD and ASD. Key topics for future research include examining developmental trajectories of co-occurring disorders, comorbid psychiatric conditions, deficits in social skills, and the nature of executive functioning impairment in individuals with co-occurring ADHD and ASD. In the current review, research in these areas is reviewed along with recommendation for future study. Given that clinicians are routinely observing and treating individuals with co-occurring symptoms, further research will yield needed information to inform intervention development and maximize benefits for affected individuals.

The utility of rat models of impulsivity in developing pharmacotherapies for impulse control disorders

High levels of impulsive behaviours are a clinically significant symptom in a range of psychiatric disorders, such as attention deficit hyperactivity disorder, bipolar disorder, personality disorders, pathological gambling and substance abuse. Although often measured using questionnaire assessments, levels of different types of impulsivity can also be determined using behavioural tests. Rodent analogues of these paradigms have been developed, and similar neural circuitry has been implicated in their performance in both humans and rats. In the current review, the methodology underlying the measurement of different aspects of impulsive action and choice are considered from the viewpoint of drug development, with a focus on the continuous performance task (CPT), stop-signal task (SST), go/no-go and delay-discounting paradigms. Current issues impeding translation between animal and human studies are identified, and comparisons drawn between the acute effects of dopaminergic, noradrenergic and serotonergic compounds across species. Although the field could benefit from a more systematic determination of different pharmacological agents across paradigms, there are signs of strong concordance between the animal and human data. However, the type of impulsivity measured appears to play a significant role, with the SST and delay discounting providing more consistent effects for dopaminergic drugs, while the CPT and SST show better predictive validity so far for serotonergic and noradrenergic compounds. Based on the available data, it would appear that these impulsivity models could be used more widely to identify potential pharmacotherapies for impulse control disorders. Novel targets within the glutamatergic and serotonergic system are also suggested.

Review of pharmacotherapy options for the treatment of attention-deficit/hyperactivity disorder (ADHD) and ADHD-like symptoms in children and adolescents with developmental disorders

Developmental disorders such as subaverage intelligence, pervasive developmental disorders, and genetic syndromes are frequently associated with comorbid attention-deficit/hyperactivity disorder (ADHD) or ADHD-like symptoms. While there are not pharmacological cures for these developmental disorders, coinciding ADHD and ADHD-like symptoms that contribute to difficulties in psychosocial functioning are frequently able to be addressed by pharmacotherapy. This article reviews what is known about the efficacy and tolerability of pharmacological interventions for the treatment of children and adolescents suffering from developmental disorders and comorbid ADHD/ADHD-like symptoms.

Advances in the treatment of attention-deficit/hyperactivity disorder: a guide for pediatric neurologists

The purpose of this article is to assist pediatric neurologists in practice and in training to better understand and distinguish between several of the most commonly prescribed treatments for attention-deficit/hyperactivity disorder (ADHD) in school-aged children. Among the various pharmacotherapies available for ADHD, 4 specific medications will be reviewed: oral release osmotic system methylphenidate hydrochloride (CON; Concerta, McNeil Pharmaceuticals), lisdexamfetamine dimesylate (LDX; Vyvanse, Shire Pharmaceuticals), atomoxetine (ATX; Strattera, Eli Lilly), and guanfacine extended-release (GXR; Intuniv, Shire Pharmaceuticals). This article contains information including medication-release pattern, administration including available dosing, adverse reactions, and case studies to serve as a guide to help determine when a particular treatment might be more appropriate than another. Although ADHD is apparent across the lifespan, this article will focus on children with ADHD from ages 6 to 12 years old. Importantly, although a number of stimulant and nonstimulant treatment options are available for school-aged children diagnosed with ADHD, choosing the best treatment options is highly dependent on obtaining thorough family and medical histories.